The pour point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbance under specified conditions. The problems associated with pour point ordinarily have to do with crude oils, heavy oils such as lubricating oils, but the recent increased use of distillate fuel oils have revealed similar problems even with these lighter, more fluid materials. Pour point problems generally arise through the formation of solid or semi-solid waxy particles in the oil.
U.S. Pat. Nos. 3,702,300 and 3,933,761 describe carboxy-containing interpolymers in which some of the carboxy groups are esterified and the remaining carboxy groups are neutralized by reaction with a polyamino compound having one primary or secondary amino group and at least one mono-functional amino group. These patents indicate that such interpolymers are useful as viscosity index improving and antisludge agents in lubricating compositions and fuels.
U.S. Pat. No. 4,284,414 discloses mixed alkyl esters made by reacting a mixture of two or more of certain monohydric alcohols with interpolymers derived from (i) alpha, beta-unsaturated dicarboxylic acids or derivatives thereof and (ii) vinyl aromatic monomers having up to 12 carbon atoms which are useful modifiers for crude oils.
U.S. Pat. No. 3,388,106 discloses copolyemrs of maleic compounds and monoethylenically unsaturated monomers which can be used as a flow-improver.
U.S. Pat. No. 4,518,509 discloses a flow improver for crude oils which are comprised of copolymers of long chain alpha-olefins with an unsaturated dicarboxylic acid, anhydride, or derivative thereof. The copolymer may be used alone or in combination with a low molecular weight linear polyethylene.
Although many pour point depressants have been suggested and many are available in the market, concerted efforts are constantly being made to find new pour point depressants which are more economical and more effective than the depressants heretofore known in the art.